chore: 添加虚拟环境到仓库

- 添加 backend_service/venv 虚拟环境
- 包含所有Python依赖包
- 注意：虚拟环境约393MB，包含12655个文件

backend_service/venv/lib/python3.13/site-packages/propcache/api.py

@@ -0,0 +1,8 @@
+"""Public API of the property caching library."""
+
+from ._helpers import cached_property, under_cached_property
+
+__all__ = (
+    "cached_property",
+    "under_cached_property",
+)